Exhaust aftertreatement system injector and control

ABSTRACT

In one aspect, an injector assembly for injecting a fluid into an exhaust aftertreatment system is provided. The injector assembly includes a housing having an outlet orifice and an inner wall defining a passageway, the passageway fluidly coupled to the outlet orifice and configured to supply the fluid to the outlet orifice, and a valve having a longitudinal axis. The valve is oriented within the passageway and configured to translate along the longitudinal axis between a first position and a second position. A downstream end of the valve includes a tapered wall oriented at a first angle with respect to the longitudinal axis, and the housing inner wall is oriented at a second angle with respect to the longitudinal axis.

FIELD OF THE INVENTION

This disclosure generally relates to exhaust treatment systems forinternal combustion engines and, more particularly, to injectors forinjecting fluid into an exhaust gas flow in an exhaust treatment system.

BACKGROUND

A diesel engine offers good fuel economy and low emission ofhydrocarbons (HCs) and carbon monoxide (CO). A mixture of air and fuelin a combustion chamber is compressed to an extremely high pressure,causing a temperature to increase until an auto-ignition temperature ofthe fuel is reached. A ratio of the air to fuel for the diesel engine ismuch leaner (more air per unit of the fuel) than it is for a gasolineengine, and a larger amount of air promotes more complete combustion andbetter efficiency of the fuel. As a result, emission of HCs and CO islower for the diesel engine than it is for a gasoline engine. However,with higher pressures and temperatures in the diesel engine, emission ofnitrogen oxides (NOx) tend to be higher because high temperatures of thecombustion chamber cause oxygen and nitrogen in intake air to combineand form the NOx.

Lower emission of NOx can be accomplished by manipulating operatingcharacteristics of the engine. For example, along with reducing outputof power and/or temperature of intake, coolant, and/or combustion,electronic controls and the injector are designed to deliver the fuel ata combination of pressure and timing of the injector and location ofspray that allows the engine to burn the fuel efficiently withoutcausing spikes in the temperature that increase the emission of the NOx.

Additionally, exhaust aftertreatment systems may be implementeddownstream of the engine. Typically, catalysts are used to treat exhaustgas from the engine and convert pollutants such as carbon monoxide, HCs,and NOx into harmless gases. In particular, to reduce NOx emissions, theaftertreatment systems may employ a selective catalytic reduction (SCR)device that reduces NOx through reduction of chemicals. SCR catalystsare currently used in diesel aftertreatment systems. The SCR device istypically fluidly connected to and positioned downstream of a dieseloxidation catalyst (DOC) with a particulate filter (PF) (e.g., a dieselPF) provided between the SCR and DOC. However, the aftertreatmentsystems may have other relative arrangements of the DOC, PF, and SCR.For example, the aftertreatment system may have a DOC/SCR/PFarrangement, or a single-catalyst combined PF and SCR. The systems mayinclude a reductant dosing system such as a diesel exhaust fluid (DEF)dosing system provided upstream of the SCR. The dosing system injects areductant such as anhydrous ammonia (NH₃), aqueous NH₃, and/or aprecursor that is convertible to NH₃ (e.g., urea ammonia or ureaCO(NH₂)₂) into a flow of exhaust gas from the engine.

The DEF is a percentage of urea in water by weight and stored in acontainer such as a tank or removable and/or refillable cartridge. TheDEF is pumped from the container and sprayed through an atomizing nozzleof the injector into the exhaust stream. Complete mixing of the urea orammonia with the exhaust and uniform distribution of the flow facilitatehigh NOx reductions.

A urea-based SCR system may utilize gaseous NH₃ to reduce the NOx.During thermolysis, heat of the gas breaks the urea down into NH₃ andhydrocyanic acid (HCNO). The NH₃ and HCNO then enter the SCR, where theNH₃ is absorbed and the HCNO is further decomposed through hydrolysisinto NH₃. When the NH₃ is absorbed, it reacts with the NOx and O₂ toproduce water and nitrogen. An amount of NH₃ injected into the exhauststream is an operating parameter. A required ratio of ammonia to NOx istypically stoichiometric and must be maintained to assure high levels ofNOx reduction.

In some known DEF dosing systems, the size of a nozzle opening of theinjector is generally constant, which may result in limited volumetricdistribution of the reductant. Further, a mass flow of the exhaust gasmay impact the spray of the urea and thus its distribution within theexhaust aftertreatment system.

Accordingly, it is desirable to provide improved SCR efficiency andreduce tailpipe NO_(x). More specifically, it is desirable to provide aDEF injector and dosing control to generate uniform area distributionand improved reductant-exhaust mixing.

SUMMARY OF THE INVENTION

In one aspect, an injector assembly for injecting a fluid into anexhaust aftertreatment system is provided. The injector assemblyincludes a housing having an outlet orifice and an inner wall defining apassageway, the passageway fluidly coupled to the outlet orifice andconfigured to supply the fluid to the outlet orifice, and a valve havinga longitudinal axis. The valve is oriented within the passageway andconfigured to translate along the longitudinal axis between a firstposition and a second position. A downstream end of the valve includes atapered wall oriented at a first angle with respect to the longitudinalaxis, and the housing inner wall is oriented at a second angle withrespect to the longitudinal axis.

In another aspect, an exhaust aftertreatment system for an internalcombustion engine is provided. The system includes an exhaust gasconduit configured to receive exhaust gas from the internal combustionengine, a selective catalytic reduction device disposed within theexhaust gas conduit and configured to receive the exhaust gas, and aninjector assembly coupled to the exhaust conduit and configured toinject a fluid into the exhaust gas. The injector assembly includes ahousing having an outlet orifice and an inner wall defining apassageway, the passageway fluidly coupled to the outlet orifice andconfigured to supply the fluid to the outlet orifice, and a valve havinga longitudinal axis. The valve is oriented within the passageway andconfigured to translate along the longitudinal axis between a firstposition and a second position. A downstream end of the valve includes atapered wall oriented at a first angle with respect to the longitudinalaxis, and the housing inner wall is oriented at a second angle withrespect to the longitudinal axis.

In yet another aspect, a method of dosing a fluid into an exhaustaftertreatment system configured to receive exhaust gas from an internalcombustion engine is provided. The method includes providing an injectorassembly having a housing and a valve translatable along a longitudinalaxis within the housing, the valve having a tapered wall oriented at afirst angle with respect to the longitudinal axis, and the housinghaving an outlet orifice and an inner wall defining a passageway, thepassageway fluidly coupled to the outlet orifice, and the inner walloriented at a second angle with respect to the longitudinal axis,providing a controller in signal communication with the injectorassembly, the controller programmed to translate the valve between aclosed position, a first open position, and a second open position, andselectively injecting the fluid through the outlet orifice and into theexhaust gas.

The above features and advantages and other features and advantages ofthe invention are readily apparent from the following detaileddescription of the invention when taken in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, advantages, and details appear, by way of example only,in the following detailed description of embodiments, the detaileddescription referring to the drawings in which:

FIG. 1 is a cross-sectional view of a prior art DEF injection assembly;

FIG. 2A is a cross-sectional schematic view of a portion of the priorart DEF injection assembly shown in FIG. 1 and in a closed position;

FIG. 2B is a cross-sectional schematic view of the prior art DEFinjection assembly shown in FIG. 2A and in an open position;

FIG. 3A is a cross-sectional schematic view of an exemplary injectionassembly according to the invention and in a closed position;

FIG. 3B is a cross-sectional schematic view of the injection assemblyshown in FIG. 3A and in a first open position;

FIG. 3C is a cross-sectional schematic view of the injection assemblyshown in FIG. 3A and in a second open position;

FIG. 4A is a bottom view of the injection assembly shown in FIG. 3A;

FIG. 4B is a cross-sectional view of the injection assembly shown inFIG. 3B and taken along line 4B-4B;

FIG. 4C is a cross-sectional view of the injection assembly shown inFIG. 3C and taken along line 4C-4C;

FIG. 5 is a cross-sectional view of an alternative injection assembly;and

FIG. 6 is a flow diagram of a method of operating the injection assemblyshown in FIGS. 3A-5.

DESCRIPTION OF THE EMBODIMENTS

The following description is merely exemplary in nature and is notintended to limit the present disclosure or its application or uses. Itshould be understood that, throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

FIGS. 1, 2A, and 2B illustrate a known diesel exhaust fluid (DEF)injector assembly 10 that generally includes an injector 11 having a tip12 that extends along a longitudinal axis ‘A’. Injector assembly 10further includes a nozzle 14 having a body 16 that defines an inlet 18(FIGS. 2A and 2B), a passageway 20, and a lower annular bottom wall 22.The bottom wall 22 defines an outlet orifice 24 at a central area of thebottom wall 22. The injector tip 12, inlet 18, passageway 20, bottomwall 22, and outlet orifice 24 are concentric with respect to eachother, and the passageway 20 is adapted to deliver an atomizing fluid 26such as urea or ammonia (FIG. 2B).

Referring to FIGS. 2A and 2B, a periphery 27 of the passageway 20 isdefined between the injector tip 12 and an inner wall 28 of the body 16and is filled with the atomizing fluid 26. The injector tip 12 isadapted to translate along the axis ‘A’ within the passageway 20 betweena closed position (FIG. 2A) and an open position (FIG. 2B). In theclosed position, the injector tip 12 obstructs the outlet orifice 24 toprevent fluid flow therethrough. In the open position, the injector tip12 allows fluid flow through the outlet orifice 24. As such, the fluid26 is sprayed out the nozzle 14 of the injector assembly 10 into astream of exhaust gas (not shown), where the fluid 26 is subsequentlymixed with the exhaust gas.

As shown in FIGS. 2A and 2B, an exterior of the body 16 is cylindricalsuch that passageway 20 has a constant diameter along axis ‘A’.Similarly, the injector tip 12 is cylindrical and has a constantdiameter within passageway 20. As such, periphery 27 between injectortip 12 and inner wall 28 is constant and only provides a constant areafor fluid flow therethrough.

FIGS. 3A, 3B, and 3C illustrate an exemplary injector assembly 100 thatgenerally includes a housing 102 and a valve 104. In the exemplaryembodiment, valve 104 translates within housing 102 along a longitudinalaxis ‘B’ to selectively inject a fluid (e.g., urea, ammonia,hydrocarbon, etc.) into an exhaust gas stream (not shown) for mixingtherewith. As shown, valve 104 translates from a closed position (FIG.3A) to a first open position (FIG. 3B) and a second open position (FIG.3C), as is described herein in more detail.

Housing 102 generally includes an outer wall 106, an inner wall 108, anda bottom wall 110. Inner wall 108 defines a passageway 112 extendingthrough housing 102 between a housing inlet end 114 and a housing outletend 116, and bottom wall 110 includes an outlet orifice 118 formedtherethrough. Housing inlet end 114 is fluidly coupled to a reservoir(not shown) configured to supply a fluid (e.g., ammonia, urea,hydrocarbon, etc.) to passageway 112. Inner wall 108 includes astraight-walled portion 120 having walls 122 and a tapered wall portion124 having tapered walls 126. As illustrated, walls 122 aresubstantially parallel, and walls 126 are tapered or converge as theyextend from housing inlet end 114 to housing outlet end 116. Taperedwalls 126 are oriented at an angle ‘α’ (FIG. 3A) with respect to axis‘B’. As such, passageway 112 is substantially cylindrical withinstraight-walled portion 120 and is substantially frusto-conical withintapered wall portion 124.

Valve 104 includes an upstream end 128 and a downstream end 130 havingan end surface 132. Downstream end 130 includes a tapered portion 134having tapered walls 136 oriented at an angle ‘β’ with respect to axis‘B’. As such, valve tapered portion 134 is substantially frusto-conical.In the exemplary embodiment, angle ‘β’ is less than angle ‘α’ such thata gap 138 is defined between housing tapered walls 126 and valve taperedwalls 136.

In operation, in the closed position (FIG. 3A), valve 104 is seatedwithin housing 102 such that valve end surface 132 blocks or obstructsoutlet orifice 118. In the closed position, end surface 132 issubstantially coplanar with housing bottom wall 110 to facilitatepreventing fluid flow through passageway 112 out through injectorassembly outlet 118 and into the exhaust gas (not shown). As illustratedin FIG. 4A, a perimeter or outer diameter 140 of valve end surface 132is sealed against a perimeter or inner diameter 142 of housing bottomwall 110 (i.e., the outer diameter of outlet orifice 118).

As injector assembly 100 moves from the closed position (FIGS. 3A and4A) to the first open position (FIGS. 3B and 4B), valve 104 istranslated along axis ‘B’ toward housing inlet end 114. In the firstopen position, valve end surface outer diameter 140 is distanced fromtapered walls 126 such that an annular opening 144 is formedtherebetween. As such, fluid may flow from housing inlet end 114,through gap 138 and annular opening 144, and subsequently through outletorifice 118 for mixing with the exhaust gas.

As injector assembly 100 moves from the first open position (FIGS. 3Band 4B) to the second open position (FIGS. 3C and 4C), valve 104 isfurther translated along axis ‘B’ toward housing inlet end 114. In thesecond open position, valve end surface outer diameter 138 is distancedfrom tapered walls 126 such that annular opening 144 is formedtherebetween. However, in the second open position, annular opening 144is enlarged compared to its size in the first open position. This is dueto tapered walls 126, 136 being oriented at the different angles ‘α’ and‘β’. More specifically, because angle ‘α’ is greater than ‘β’, housingtapered walls 126 and valve tapered walls 136 diverge as they extendfrom housing bottom wall 110 toward housing inlet end 114. As such, thedistance between valve outer diameter 140 and housing tapered walls 126increases the further valve 104 is translated along axis ‘B’ away fromhousing bottom wall 110, which increases the outer diameter of annularopening 144 and thus increases the area through which fluid may flow.

Due to the angular orientation of housing tapered walls 126 with respectto valve tapered walls 136, the outer diameter of annular opening 144increases as valve 104 moves from the closed position toward housinginlet end 114. For example, in the closed position, annular opening 144is not present (see FIG. 4A). As valve 104 moves to the first openposition, annular opening 144 has an outer diameter ‘D1’ (see FIG. 4B).As valve 104 moves further toward inlet end 114 to the second openposition, annular opening 144 has increased in size to have an outerdiameter ‘D2’.

As illustrated, ‘D2’ is greater than ‘D1’ such that the size of annularopening 144 in the second open position is greater than the size ofannular opening 144 in the first open position. As such, the spraypattern (e.g., fluid droplet-size distribution) may change with thedifferent opening areas of annular opening 144. Although injectorassembly 100 is only shown in the first and second open positions, valve104 may be translated or opened to any desired position from the closedposition toward the housing inlet 114 to a maximum open position (notshown). Accordingly, the diameter of annular opening 144, and thus thevolumetric flow of fluid, may be selectively controlled or varied forinjection of a desired spray pattern (droplet size distribution) intothe exhaust gas. Moreover, angles ‘α’ and ‘β’ may be varied to provide adesired size of annular opening 144 at a given location of valve 104along axis ‘B’. In the exemplary embodiment, angles ‘α’ and ‘β’ areacute angles. Alternatively, angles ‘α’ and ‘β’ may be obtuse, whichfacilitates adjusting annular opening 144 with a relatively smallerchange in vertical position of valve 104.

A controller 150 may control operation of injector assembly 100. In theexemplary embodiment, controller 150 is a dedicated control for injectorassembly 100. However, controller 150 may be any suitable controllerthat enables injector assembly 100 to function as described herein. Forexample, controller 150 may be a vehicle controller. As used herein, theterm controller refers to an application specific integrated circuit(ASIC), an electronic circuit, a processor (shared, dedicated, or group)and memory that executes one or more software or firmware programs, acombinational logic circuit, and/or other suitable components thatprovide the described functionality.

Controller 150 is programmed to translate valve 104 along axis ‘B’ tovary the size of annular opening 144, and to supply the fluid toinjector assembly 100 at a desired pressure. In one embodiment,controller 150 is programmed to size the nozzle open area 144 directlyproportional to an amount of pressure of the fluid that injectorassembly 100 injects into the exhaust gas. Alternatively, controller 150may supply the fluid to injector assembly 100 at a constant pressure.

Because nozzle open area 144 and injection pressure are variable, alength of penetration of the spray of the atomizing fluid out of outletorifice 118 is variable. Additionally, the injection pressure and nozzleopen area 144 are variable to provide different sized droplets of thefluid into the exhaust gas. For example, controller 150 may controlurea-dosing based upon a flow rate of the exhaust. In a low exhaustflow, fluid may mix more uniformly with the exhaust gas when the fluiddroplet size is relatively small. As such, controller 150 may beprogrammed to reduce the size of nozzle open area 144 and the injectionpressure to reduce the spray-penetration distance, which improves SCRefficiency in the low exhaust flow. Conversely, in a high exhaust flow,fluid may mix more uniformly with the exhaust gas when the fluid dropletsize is relatively large. As such, controller 150 may be programmed toincrease the size of nozzle open area 144 to increase thespray-penetration distance, which improves SCR efficiency in the highexhaust flow.

FIG. 5 illustrates an alternative injection assembly 160 that is similarto injection assembly 10 shown in FIGS. 3A-3C, except housing 102includes a second straight-walled portion 162 and valve 104 includesdownstream walls 164. Straight-walled portion 162 includes walls 166downstream of tapered wall portion 124 and proximate outlet orifice 118,and downstream walls 164 are oriented downstream of tapered walls 136and proximate valve end surface 132. In the exemplary embodiment,downstream walls 164 and walls 166 are substantially parallel to axis‘B’. However, walls 164, 166 may be oriented at any suitable angle thatenables injection assembly 160 to function as described herein.

FIG. 6 illustrates a urea-dosing-control method 200 for improvingurea-exhaust mixing. The operation of injector assembly 100 (involvingnozzle open area 144 and fluid injection pressure) may be varied basedon the exhaust gas flow rate, and the exemplary method compensates forimpact of such rate on the spray to allow for a more uniformdistribution of the urea spray in a greater range of the rate. As such,the method controls the operation of injector assembly 100 based upon anengine operation condition.

Method 200 includes, at step 202, determining the exhaust gas flow rate.In the embodiment shown, the rate is determined by any suitable sensorsuch as an electronic-control unit (ECU) or a mass flow sensor (notshown). At step 204, controller 150 determines if the measured mass flowrate of the exhaust gas is a low measured flow rate or a high measuredflow rate based on the measured flow rate.

If controller 150 determines the measured flow rate is a low exhaust gasflow rate, at step 206, controller 150 adjusts injector assembly 100 tohave a relatively smaller nozzle open area 144. For example, controller150 may position valve 104 in the first open position (FIG. 3B).However, if controller 150 determines the measured flow rate is a highexhaust gas flow rate, at step 208, controller 150 adjusts injectorassembly 100 to have a relatively larger nozzle open area 144. Forexample, controller 150 may position valve 104 in the second openposition (FIG. 3C).

As such, at step 206 and/or step 208, controller 150 adjusts injectorassembly 100 to vary the fluid droplet size as a function of at leastthe injection pressure and/or and nozzle open area 144. Alternatively oradditionally, at step 210, the desired nozzle open area and injectionpressure can be calculated by use of a calibration table.

Described herein is an injector assembly and method for varying fluidinjection into an exhaust gas stream. The injector assembly includeshousing inner walls and valve walls oriented at different angles suchthat the inner walls and the valve walls diverge. The position of thevalve may be varied to vary the size of an annular opening formedbetween the valve and housing inner walls. As such, the amount of fluidflow through an outlet orifice may be varied. In addition, the fluidinjection pressure may be varied. As such, the fluid droplet size andspray penetration into the exhaust gas may be varied depending onconditions in an exhaust gas aftertreatment system. The system thuscompensates for the impact of the exhaust-flow rate on the urea spraydistribution and allows for more uniform spray distribution in a greaterexhaust flow rate range. This results in reduced tailpipe NO_(x)emission with improved urea mixing at varying exhaust gas flowconditions.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiments disclosed, but that theinvention will include all embodiments falling within the scope of theapplication.

What is claimed is:
 1. An injector assembly for injecting a fluid intoan exhaust aftertreatment system, the injector assembly comprising: ahousing having an outlet orifice and an inner wall defining apassageway, the passageway fluidly coupled to the outlet orifice andconfigured to supply the fluid to the outlet orifice; and a valve havinga longitudinal axis, the valve oriented within the passageway andconfigured to translate along the longitudinal axis between a firstposition and a second position, wherein a downstream end of the valveincludes a tapered wall oriented at a first angle with respect to thelongitudinal axis, and the housing inner wall is oriented at a secondangle with respect to the longitudinal axis.
 2. The injector assembly ofclaim 1, wherein the second angle is larger than the first angle.
 3. Theinjector assembly of claim 1, wherein the first and second angles areacute angles.
 4. The injector assembly of claim 1, wherein the valvefurther includes an end surface and the housing further includes abottom wall, and wherein in the first position the valve is orientedsuch that end surface is positioned within the outlet orifice and thevalve end surface is substantially coplanar with the housing bottomsurface.
 5. The injector assembly of claim 4, wherein in the secondposition the valve is oriented such that an annular opening is definedbetween the valve downstream end and the housing inner wall.
 6. Theinjector assembly of claim 5, wherein the valve is configured totranslate to a third position between the first position and the secondposition, and wherein in the third position the valve is oriented suchthat a second annular opening is defined between the valve downstreamend and the housing inner wall.
 7. The injector assembly of claim 6,wherein the second annular opening is smaller than the annular openingin the second position.
 8. The injector assembly of claim 1, wherein thefluid is at least one of ammonia, urea, and hydrocarbon.
 9. The injectorassembly of claim 1, wherein the fluid is urea, and further comprising aurea reservoir fluidly coupled to the passageway to supply the ureathereto.
 10. An exhaust aftertreatment system for an internal combustionengine, the system comprising: an exhaust gas conduit configured toreceive exhaust gas from the internal combustion engine; a selectivecatalytic reduction device disposed within the exhaust gas conduit andconfigured to receive the exhaust gas; and an injector assembly coupledto the exhaust conduit and configured to inject a fluid into the exhaustgas, the injector assembly comprising: a housing having an outletorifice and an inner wall defining a passageway, the passageway fluidlycoupled to the outlet orifice and configured to supply the fluid to theoutlet orifice; and a valve having a longitudinal axis, the valveoriented within the passageway and configured to translate along thelongitudinal axis between a first position and a second position,wherein a downstream end of the valve includes a tapered wall orientedat a first angle with respect to the longitudinal axis, and the housinginner wall is oriented at a second angle with respect to thelongitudinal axis.
 11. The system of claim 10, wherein the second angleis larger than the first angle.
 12. The system of claim 10, wherein thefirst and second angles are acute angles.
 13. The system of claim 10,wherein the valve further includes an end surface and the housingfurther includes a bottom wall, and wherein in the first position thevalve is oriented such that end surface is positioned within the outletorifice and the valve end surface is substantially coplanar with thehousing bottom surface, and in the second position the valve is orientedsuch that an annular opening is defined between the valve downstream endand the housing inner wall.
 14. The system of claim 10, wherein thefluid is urea, and further comprising a urea reservoir fluidly coupledto the passageway to supply the urea thereto.
 15. A method of dosing afluid into an exhaust aftertreatment system configured to receiveexhaust gas from an internal combustion engine, the method comprising:providing an injector assembly having a housing and a valve translatablealong a longitudinal axis within the housing, the valve having a taperedwall oriented at a first angle with respect to the longitudinal axis,and the housing having an outlet orifice and an inner wall defining apassageway, the passageway fluidly coupled to the outlet orifice, andthe inner wall oriented at a second angle with respect to thelongitudinal axis; providing a controller in signal communication withthe injector assembly, the controller programmed to translate the valvebetween a closed position, a first open position, and a second openposition; and selectively injecting the fluid through the outlet orificeand into the exhaust gas.
 16. The method of claim 15, further comprisingproviding the injector assembly with the second angle being larger thanthe first angle.
 17. The method of claim 15, further comprising:providing a selective catalyst reduction device in the exhaustaftertreatment system downstream of the injector assembly; and supplyingurea as the fluid to the injector assembly to selectively inject ureainto the exhaust gas.
 18. The method of claim 15, further comprising:measuring a mass flow rate of the exhaust gas in the exhaustaftertreatment system; and selectively injecting, with the injectorassembly, a predetermined amount of fluid into the exhaust gas based onthe measured mass flow rate of the exhaust gas.
 19. The method of claim15, further comprising: measuring a mass flow rate of the exhaust gas inthe exhaust aftertreatment system; determining, with the controller,whether the measured mass flow rate is a low mass flow rate or a highmass flow rate; moving the valve to the first open position if themeasured mass flow rate is the low mass flow rate, the first openposition defining a first annular opening between a downstream end ofthe valve tapered wall and the housing inner wall; and moving the valveto the second open position if the measured mass flow rate is the highmass flow rate, the second open position defining a second annularopening between the downstream end of the valve tapered wall and thehousing inner wall, wherein the second annular opening is larger thanthe first annular opening.